Polycomb Repressive Complex 2 (PRC2) regulates gene expression through the trimethylation of lysine 27 of histone H3 (H3K27me3). PRC2 is required for long-term epigenetic silencing of chromatin and plays an important role in stem cell differentiation and early embryonic development. Interestingly, misregulation of PRC2 is associated with disease. Overexpression of EZH2, the methyltransferase catalytic subunit of PRC2, is associated with cancer progression. However, how PRC2 is regulated is unknown. Recent findings indicate that PRC2 associates with thousands of lncRNA, which are proposed to serve as cofactors for PRC2 function. A large number of these PRC2-associated lncRNAs are transcribed from clinically important loci, suggesting a role for RNA in the defective expression of PRC2 in disease. However, little is known about the molecular biology of PRC2-associated transcripts, as well as about the RNA determinants for PRC2 association. Therefore, the main goals of this proposal are to determine the RNA requirements for association and targeting of PRC2, as well as to characterize the molecular origin and stability of the PRC2- associated lncRNAs to gain insight into the mechanisms of targeting and regulation of PRC2. Because of the importance of PRC2 regulation in health and disease, the conclusions from this research will have the potential to be applied in the solution of clinically relevant problems. PUBLIC HEALTH RELEVANCE: PRC2 is critical for long-term epigenetic silencing of chromatin. It plays a major role in the differentiation of stem cells, early embryonic development and carcinogenesis. Due to its importance in health and disease, the regulation of PRC2 has direct implications for clinically relevant problems.